Photographic material is conventionally constructed as a multilayered element including an electrically insulating support and photographic light-sensitive emulsion layers. This photographic material is susceptible to accumulation of electrostatic charges caused by repeated frictional contacts between the photographic material with surfaces of the same or different kinds of materials, or during peeling operations performed in order to separate superposed materials of the same or different kinds during the manufacture of, or use of, the photographic material. These accumulated electrostatic charges can cause many problems. The most serious problem being that the light-sensitive emulsion layers can be inadvertently sensitized by the discharge of these accumulated electrostatic charges before development processing is performed which results in the generation of dot-like spots, or dendritic or feather-like streaks in the development processed photographic film. These spots and streaks are generally called static marks, and considerably diminish, if not destroy, the commercial value of the photographic film.
Further, these accumulated electrostatic charges are also responsible for other problems. For instance, since the electrostatic charge-accumulated film surface on a photographic film is subject to dust particle adhesion, application of a uniform coating on the electrostatic charge-accumulated surface is not possible.
Generation of electrostatic charges is, as described above, due to physical contact and separation operations encountered in the course of the production of photographic materials, and due to physical contact and separation of a photographic film with a wide variety of machine parts inside an automatic camera. In recent years in particular, photographic materials have been designed so as to have higher photographic speed and are frequently subjected to harsh treatments such as high speed coating, high speed photographing, high speed processing with an automatic developing machine, for example, which have increased the potential for the generation of static marks. In addition, processed films have been subject to dust adhesion during handling in various ways.
In order to eliminate these problems, it is desirable to add an antistatic agent to a photographic material. However, conventional antistatic agents generally employed in other fields cannot necessarily be applied to photographic materials due to requirements unique to photographic material technology. In this regard, antistatic agents to be used in photographic materials are required to possess not only excellent ability to prevent electrification but also other important properties. For example, the antistatic agent cannot have adverse effects on other photographic characteristics including sensitivity, fog, graininess, sharpness, film strength and adhesiveness of photographic materials. Also, the antistatic agent cannot contaminate processing solutions for photographic materials and can not hasten the fatigue of such processing solutions; it cannot pollute carrier rollers, and it cannot lower the adhesion power between each pair of adjacent constituent layers, for example.
One method for the elimination of problems arising from static electricity consists in designing a photographic material such that electric conductivity of the photographic material's surfaces may be enhanced to enable accumulated electrostatic charges to be scattered and lost in a short time before the discharge occurs. In particular, this method becomes an effective measure against dust adhesion after processing.
Therefore, a wide variety of methods for increasing electrical conductivities of a support and every sort of coating provided at the surface of a photographic material have been previously proposed, and utilization of various hygroscopic substances, water-soluble inorganic salts, certain kinds of surface active agents and polymers, and so on, have been attempted.
However, these electrical conductivity increasing substances each suffer from their own individual disadvantages. For example, some of these substances are specific in their ability depending on the kind of a film support used and the variation in photographic composition used, and some of them lose electrical conductivities after processing which allows dust adhesion, and some of them have humidity sensitivity resulting in generation of static marks under a low humidity condition, and some of them cause a deterioration in other photographic properties such as coating facility and transparency, and some of them adversely affect adhesiveness of the photographic film, and others contaminate a development processing solution used. Consequently, the application of such substances to photographic materials has proven difficult.